Expression of ia antigens by murine keratinizing epithelial langerhans cells

Modulation of Ia+ Langerhans cell numbers in vivo by cultured epidermis derived supernatants and by GM-CSF

This paper demonstrates that epidermal cells in culture produce an activity which can increase the frequency of Ia+ epidermal Langerhans cells (LC). This was achieved by treating mice topically with a mixture containing supernatant derived from primary culture of murine epidermis (ES) and a synthetic corticosteroid, triamcinolone acetonide (TAC). The presence of the supernatant in the mixture partially protected the Ia+ LC from depletion by the steroid. The Ia+ LC frequency increasing activity was measured as the difference between the Ia+ LC frequency due to treatment with steroid mixed with supernatant and the Ia+ LC frequency due to treatment with steroid mixed with negative control medium. The mean frequency of Ia+ LC in epidermis treated with TAC mixed with ES was 606(SD 43) cells/mm2, as compared with 486 (SD 68) cells/mm2 in the epidermis treated with TAC mixed with control medium. The activity appeared to be caused by (a) proteinaceous factor(s). A fraction of ES which was retained above a > or = 10 KDa molecular weight cut-off membrane was capable of partially protecting Ia+ LC frequency from TAC depletion. Supernatants from cultured lymph nodes, dermis as well as the squamous cell carcinoma lines T7 and T79, but not the human osteosarcoma cell-line 143B, also contained similar activities. We demonstrate that GM-CSF also increased the number of Ia+ epidermal LC when applied topically to mouse skin in this system. Therefore, using this Ia+ LC frequency modulation system, we propose that GM-CSF is one example of a cytokine which may be involved in the regulation of Ia+ LC numbers in epidermis and that epidermal cells produce factors which can increase the number of Ia+ LC.

The hamster cheek pouch: an immunologically privileged site suitable to the study of granulomatous infections

The hamster cheek pouch is an invagination of oral mucosa, characterized histologically as skin-like. In this paper we describe anatomical, histological and embriological features of the pouch and comment on the pouch as an immunologically privileged site since it lacks lymphatic drainage and has few Langerhans cells. We present the review from literature and our observations after inoculation in the pouch of mycobacteriae (BCG, Mycobacterium tuberculosis and Mycobacterium leprae) and a fungus (Paracoccidioides brasiliensis). Lesions in the pouch were granulomatous but smaller and long lasting; even granulomatous, the reaction was inefficient to control the proliferation of agents compared with inoculation in other sites, except for BCG. Appearance of immunity was also delayed or absent and, when it was detected, a sharp decrease in number of agents in pouch lesions was observed. These observations make the pouch an interesting site for the study of the role of immune system in infectious diseases and in granuloma formation.

Identification of CD4+, 2H4+ (T8 gamma +) suppressor-inducer cells in normal human epidermis and superficial dermis

Immunohistological staining of frozen sections of normal human skin demonstrated the presence of significant numbers of mononuclear cells expressing novel epitopes associated with CD4-positive suppressor-inducer functions. The cells were located around superficial vessels and within the basal layers of the epidermis and hair follicles. The antigen identified by the various antibodies has been shown to be functionally important in the induction of various suppressor cells capable of abrogating B cell responses to pokeweed mitogen. The presence in the skin of cells with possible down-regulatory functions in the immune response may be significant with respect to surveillance against neoplasms and control of appropriate responses to infectious agents.

The sequential demonstration of non-specific esterase reactivity Ia antigen and Thy-1 antigen in murine epidermal sheets

Immunofluorescence demonstrating Ia and Thy-1 antigens and non-specific esterase (NSE) enzyme histochemistry were performed sequentially on sheets of ear epidermis from CBA, C3H.OH, A/J, and Balb/c mice. The same areas of epidermis were photographed after each reaction and individual cells identified and compared. Thy-1+ dendritic cells expressed neither Ia antigen nor NSE reactivity. No cell was found to express Ia antigen or NSE alone: thus all Langerhans cells (LC) in normal murine epidermis appeared to co-express Ia antigen and NSE reactivity. LC expressing greatly increased amounts of Ia antigen were occasionally seen apposed to Thy-1+ cells suggesting that these cells may be immunologically active--perhaps involved in antigen presentation.

Regulation by the skin of lymphoid cell recirculation and localization properties

The existence of epidermal Langerhans cells, Ia-positive dermal dendritic cells, lymphocytes which can demonstrate epidermitropism, and keratinocytes capable of secreting Interleukin-1-like molecules, each support the concept that skin can function as an immunologic organ. Such conclusions are further strengthened by the knowledge that both afferent and efferent immune responses can take place exclusively within the skin. The purpose of our study was to evaluate the ability of skin to regulate lymphoid cell recirculation and localization properties. The use of ultraviolet radiation as an exogenous stimulus resulted in a pronounced redistribution of antigen-presenting cells from central (spleen) to peripheral (skin and lymph node) lymphoid tissues as well as marked increase in the rate of lymphocyte entry into skin draining lymph nodes. This latter condition was due to elevations in the quantitative levels of high endothelial venules present within the peripheral lymph nodes. The ability of epidermal keratinocytes to express Class II molecules is known to be associated with a number of skin diseases. However, the functional significance of this phenomenon is unknown. The results of our studies, employing a nude mouse model, indicate that the expression of Class II molecules by keratinocytes facilitates the movement of Langerhans cell precursors into the epidermis and may also function to enhance lymphocyte entry into the skin. We conclude that nonlymphoid components resident within the skin can influence essential aspects of the adaptive immune response through the production of soluble factors (e.g., Interleukin-1 or through the cellular expression of Class II molecules.

Alpha tocopherol alters the distribution of Langerhans cells in DMBA-treated hamster cheek pouch epithelium

Thirty-seven adult male and female golden hamsters (Mesocricetus auratus) were divided into four experimental groups. In Group A, the animals served as untreated controls, having the left buccal pouches painted with mineral oil. In Group B, the animals received 10 mg vitamin E (alpha tocopherol) in peanut oil by the oral route, with a fine pipette, twice weekly. In Group C animals, the left buccal pouch was painted three times weekly with DMBA (0.5% solution of 7,12 dimethylbenz(a)anthracene in heavy mineral oil). Group D animals received both vitamin E and DMBA in the amounts indicated for Groups B and C, with the vitamin E being administered on days alternate to the DMBA painting, also in the manner described for the above groups. All animals were killed after eight weeks of treatment. Epithelial whole mounts were prepared from the left buccal pouches. These specimens were then stained for ATPase to demonstrate the presence of Langerhans cells (LCs). A notably decreased density of LCs was observed after treatment with DMBA. Vitamin E administration in addition to DMBA treatment resulted in a less dramatic decrease in LC density. Since vitamin E has been shown to retard experimental oral carcinogenesis, vitamin E may retard carcinogenesis by maintaining the number of Langerhans cells.

Effects of smokeless tobacco and snuff on oral mucosa of experimental animals

The effects of smokeless tobacco on oral mucosa were studied in 60 Syrian hamsters. Histologic study of the buccal pouch mucosa revealed no significant pathologic changes at either ten or 20 weeks after the start of the experiment. However, studies on epithelial whole mounts revealed a statistically significant decrease in mitotic activity and a statistically significant increase in the number of Langerhans' cells in animals subjected to daily use of tobacco or snuff for 20 weeks.

RA can alter the distribution of ATPase-positive Langerhans cells in the hamster cheek pouch in association with DMBA application

Thirty-six young adult male and female Syrian hamsters were divided into four groups. Group 1 (N = 6) was treated with mineral oil, Group 2 (N = 12) was treated with 7,12-dimethylbenz[a]anthracene (DMBA), Group 3 (N = 12) was treated with DMBA and 13-cis-retinoic acid (RA), and Group 4 (N = 6) was treated with RA only. The hamsters were treated three times a week for six weeks. When the DMBA-treated animals were also treated with RA, tumor formation was inhibited. In the DMBA-treated animals that did not have RA, there was a significant reduction in the number of Langerhans cells (LCs) located interfocally and in foci compared with controls (p less than or equal to 0.001). The systemic administration of 10 mg of RA significantly increased the number of ATPase-positive LCs in the focal aggregates (p less than or equal to 0.001). Interfocally, the number of ATPase-positive LCs was statistically elevated in pouches from RA- and DMBA-treated animals (Group 2 vs. Group 3, p less than or equal to 0.01). Following the administration of RA (Group 4), there was a statistically significant increase of LCs interfocally compared with Groups 2 or 3 (p less than or equal to 0.001). RA administered alone resulted in a small increase in foci compared with Group 3 but in a significant decrease compared with the control group (p less than or equal to 0.001). Systemic RA appears to not only affect the number of ATPase-positive LCs but also to alter the distribution of these cells in DMBA-treated pouches.(ABSTRACT TRUNCATED AT 250 WORDS)

Langerhans cells: antigen presenting cells of the epidermis

While epidermis in the skin provides an excellent barrier to the environment, it is an incomplete one. Some antigenic material can penetrate through the stratum corneum (or be introduced pathologically) where strategically placed epidermal Langerhans cells reside. In this review, we have assembled relevant data concerning the antigen presenting potential of epidermal Langerhans cells. Strong circumstantial evidence derived from in vitro studies of epidermal cell suspensions enriched for Langerhans cells indicates that Langerhans cells possess this capability. In vivo studies with intact skin indicate that critical numbers of functioning Langerhans cells are essential for successful induction of contact hypersensitivity by epicutaneously applied haptens. And within the past several months, experiments with purified preparations of epidermal Langerhans cells have proven that these cells, and perhaps they alone among epidermal cells, possess the capacity of processing and presenting haptenic determinants to the immune system. The challenge for the future is to determine the extent to which this unique property of Langerhans cells affords physiologic protection to the skin and under what pathologic circumstances altered Langerhans cell function leads to disease.

Dynamic changes in epidermal Ia-positive cells in allergic contact sensitivity reactions in mice

In mice sensitized with trinitrochlorobenzene, serial changes in epidermal Ia-positive cells were studied at various times after challenge. Until 3 days post-challenge, the Ia-positive cells consisted only of dendritic Langerhans cells; their number was decreased but they were significantly enlarged, with extending dendrites. Some Langerhans cells were also found surrounding a hair follicle, extending their dendrites toward the follicle like the spokes of a wheel. From 3 to 9 days after challenge, keratinocytes also began to express Ia antigens in the epidermis in addition to Langerhans cells, whose size diminished. This suggests that there are two phases in the response of the epidermal Ia antigens in contact sensitivity reactions, i.e. an early phase in which enlarged Langerhans cells are the only Ia-positive cells in the epidermis, and a late phase in which keratinocytes take over as the major Ia-positive cells, while Langerhans cells resume their original size. Ia antigen expression on keratinocytes in this late phase probably plays a crucial role in completely eliminating allergens deposited on the keratinocytes.

Acute effect of DMBA application on Langerhans cells of the hamster buccal pouch mucosa

One, two, and three applications of DMBA in mineral oil to hamster buccal pouch mucosa did not result in obvious histologic alterations in experimental periods ranging from 4 1/2 hours to 2 weeks after the last DMBA application. However, there were significant increases in the number of Langerhans cells, as disclosed histochemically with ATPase staining. There was also an increase in the length and size of the dendritic processes of the Langerhans cells. Applications of DMBA in oil resulted in a consistently significant increase in Langerhans cells when compared to the buccal pouch mucosa of untreated animals. However, mineral oil applications also resulted in a slight increase in Langerhans cells when compared to the mucosa of untreated controls. The major effects of the DMBA on Langerhans cells occurred after 2 weeks and with increasing numbers of applications. The increase in Langerhans cells is interpreted as an enhanced response by immunologically competent cells which may represent an early immune response to the very early changes in carcinogenesis.

Dynamics of Langerhans cells in genetically defined murine epidermal cell culture

Unlike keratinocytes, Langerhans cells express both surface ATPase activity and Ia (HLA-DR) antigens. A well-characterized in vitro system containing Langerhans cells would be of great use in elucidating their functions. Thus, epidermal cell cultures derived from neonatal Balb/c mice were examined for the presence of Langerhans cells. Twenty-four hours after initiation of culture, ATPase- and Ia-positive cells were seen to be associated with cell aggregates. By day 3, Langerhans cells migrated on to the substratum and, as the cultures matured and stratified, were seen both in groups and as single cells for the duration of the cultures (day 14). During culture, although the total number of cells increased, the percentage of cells expressing Ia antigen and ATPase activity remained constant, suggesting that Langerhans cells increase in number during cell culture. Such a situation could arise from actual division of Langerhans cells during culture or from latent expression of Ia antigen and ATPase activity by pre-existing cells. This is the first study of the dynamics of Langerhans cells in a cell culture system and shows that Langerhans cells are present throughout the lifespan of the cultures.

Influence of Langerhans cells on the survival of H-Y incompatible skin grafts in rats

Evidence is presented that Langerhans cells (LCs) play an important role in the rejection of H-Y incompatible skin grafts in BN rats. Not only are small male trunk skin isografts much more likely to be rejected by BN females than similarly sized male foot pad, tail, and ear skin transplants, all of which possess fewer LCs than trunk skin, but the survival of male trunk skin grafts can be prolonged by replacing their LC population with allogeneic female cells.

Variable expression of Ia antigens on the vascular endothelium of mouse skin allografts

Ia antigens are membrane-bound glycoproteins that play a part in antigen recognition and subsequent cell-cell interactions in the immune response. In the mouse they are coded for by the I region of the major histocompatibility complex H-2 and have been demonstrated on B lymphocytes, monocytes, activated T cells, macrophages and dendritic cells, including Langerhans cells. Ia-like antigens have also been detected on the vascular endothelium in man and on epidermal keratinocytes in rats but expression on the latter cells was induced by a graft-versus-host reaction or by contact hypersensitivity. In the mouse, previous studies have suggested that Ia antigens in skin are restricted to epidermal Langerhans cells and it was thought that these were the targets for Ia-dependent rejection of skin allografts. The results presented here show that Ia antigens in mouse allografts are also present on the vascular endothelium but their expression is variable and dependent on the immunological status of the recipient. These findings suggest that vascular endothelial cells can act as targets in Ia-incompatible skin allograft rejection.

Corneal allograft rejection. The role of the major histocompatibility complex

The greater success of corneal transplantation compared to other organ transplants has led to the concept that the cornea is a site of "immunological privilege." Corneal cells possess the antigens of the major histocompatibility complex responsible for allograft rejection in other tissues (i.e., HLA antigens). The avascularity of the cornea accounts for the relative protection of the donor cornea from the immunological surveillance of the recipient. As the roles and functions of the major histocompatibility complex are unravelled, the mechanisms responsible for host sensitization, lymphocyte activation and allograft rejection are becoming better understood. In particular, the HLA-DR antigen in humans is believed to play an integral part in allograft rejection. Langerhans cells in human corneal epithelium have been shown to bear this antigen. Evidence suggests that these cells or similar HLA-DR-bearing cells in the cornea play a major role in corneal allograft rejection. In light of these advances in transplantation immunobiology, new methods of suppressing and possibly preventing allograft rejection in corneal transplantation are presented.

Retardation of experimental oral cancer development by retinyl acetate

Sixty young adult Syrian hamsters were divided into five groups. Group 1 and Group 2 animals were treated with 0.25% dimethylbenz(a)anthracene (DMBA), painted on their left buccal pouches thrice weekly for 20 weeks. Starting at 12 weeks, at which time there was clinical evidence of leukoplakia and initial tumor formation, Group 2 animals received 10 mg retinyl acetate 3 times/week in a 5% solution in peanut oil, while Group 1 animals received only peanut oil. Two animals in Group 1 and two animals in Group 2 were sacrificed weekly from week 12 to week 20. Left buccal pouches were examined, tumors were counted, and tumor size was measured. Group 3 animals were untreated controls, Group 4 animals were retinyl acetate controls, and Group 5 animals received only peanut oil. It was found that DMBA-treated animals receiving retinyl acetate from week 12 to week 20 developed fewer tumors, and their average tumor size was less than that in DMBA-treated animals not receiving retinyl acetate. It appears that retinyl acetate, administered systemically, can retard tumor development even after leukoplakia has been established and tumors have begun to develop.

Two-phase carcinogenesis in hamster buccal pouch

A two-phase mechanism of chemical carcinogenesis in hamster buccal pouch has been demonstrated. Painting of buccal pouches three times weekly with a 0.1 percent solution of 7,12-dimethylbenz(a)anthracene (DMBA) in mineral oil for 10 weeks resulted in no visible tumors nor any microscopic evidence of dysplasia after the animals had been maintained for a 20 week period (Group 1 animals). Painting with 0.1 percent DMBA for 10 weeks, no treatment for a following 6 week period, and painting with 0.5 percent DMBA for a subsequent 4 weeks resulted in epidermoid carcinomas (Group 2 animals). Painting with 0.5 percent DMBA for 4 weeks in animals without prior treatment resulted in no tumors (Group 3 animals). It is postulated that the early treatment in Group 2 may serve for initiation and the later treatment for promotion.

Differential distribution of Langerhans cells in organ culture of human skin

Epidermal Langerhans cells (LCs) function as the antigen-presenting cells in such cutaneous cell-mediated immune responses as contact hypersensitivity and in the mixed epidermal cell-lymphocyte reaction. They have also been implicated in the immune response in skin allograft rejection. Since organ culture of thyroid and pancreas has been shown to prolong allograft survival, presumably through the loss of antigen-presenting cells, we examined the effect of skin explant culture on LC survival. Human skin explants were placed in organ culture and examined serially as whole mounts of epidermis for the presence of LCs as judged by ATPase activity, and OKT-6 and HLA-DR antigens. Although we observed morphologic changes and an absolute reduction in the number of positively stained cells, culture for up to 28 days failed to deplete explants of these cells. Langerhans cells were also sought in the epidermal outgrowths that develop peripheral to the original explants. They were never seen in the area beyond 0.3 mm from the explant edge. Organ culture of skin thus provides a means to explore the contribution of LCs to skin allograft rejection by comparing the immunogenicity of epidermal portions of the explant with the epidermal outgrowth.

Reactivity of epidermal Langerhans cells to a histochemical method for demonstration of beta-glucuronidase

Sheets or sections of mouse epidermis reacted by a histochemical method for the enzyme beta-glucuronidase display a subpopulation of dendritic cells which correspond in number and spacing to Langerhans cells demonstrated by reactivity for ATPase or Ia antigens. A similar staining pattern is seen in rat, rabbit, and guinea pig epidermis. In rhesus monkey and human skin, Langerhans cells appear to be reactive for beta-glucuronidase but, as keratinocytes are also reactive, Langerhans cells are not readily identifiable by this method. The thermal stability of beta-glucuronidase differs between strains of mice. Langerhans cells of Balb/C and C3H strains can thus be distinguished by appropriate pretreatment before incubation, a method of potential value for experimental investigations of the origin of Langerhans cells.

Biochemical documentation of allelic variation of the I-E antigens of the d, k, p, r, and u haplotypes

The extent of allelic variation of the E alpha and E beta polypeptide chains of the I-E antigens from the H-2d, H-2k, H-2p, H-2r, and H-2u haplotypes is described. E alpha and E beta chains were individually labeled with arginine or lysine and compared by tryptic peptide analysis. The results indicate minimum variability among the E alpha polypeptides encoded by the d, k, p, and r haplotypes. However, the Eu alpha chain differed significantly from the other allelic E alpha gene products. On the other hand, the E beta alleles demonstrated substantial variability with the Ed beta being notably less similar to the other alleles than they are to each other. These findings are consistent with a number of observations regarding the serology and functions of the I-E antigens.

Analysis of neonatally induced tolerance of H-2 alloantigens. I. Adoptive transfer indicates that tolerance of class I and class II antigens is maintained by distinct mechanisms

Neonatal inoculation of mice with semi-allogeneic lymphohematopoietic cells produces a state of highly specific allograft tolerance. Phenotypically, by both in vivo and in vitro criteria, antigen-reactive cells specific for the tolerated antigens appear to be clonally deleted from intact, tolerant mice. However, a series of adoptive transfer experiments using mice rendered tolerant of various H-2 alloantigens revealed that tolerance of Ia (class II) antigens is maintained by a different mechanism than tolerance of K/D (class I) antigens. Long-term acceptance of Ia-disparate grafts by recipients of Ia-tolerant lymphoid cells suggested that an active process (rather than passive clonal deletion) mediates and maintains this type of tolerance. No comparable success was achieved when tolerance of isolated class I or entire H-2 haplotype disparity was examined, suggesting that clonal deletion might be operative in these combinations. Modest prolongation of skin-graft survival was observed in adoptive transfer recipients of lymphoid cells from donors tolerant of I-JECSD disparity. These data are compatible with the hypothesis that the central I region (JE) promotes tolerance induction to associated strong IA- and D-region alloantigens by activating a suppression mechanism.

Distribution of Langerhans cells in normal and carcinogen-treated mucosa of buccal pouches of hamsters

The distribution of Langerhans cells in normal and carcinogen-treated mucosa of buccal pouches of hamsters was studied. Decrease in density and in focal aggregates of Langerhans cells and loss of their complex dendritic networks were found in carcinogen-treated mucosa.

Langerhans cell function dictates induction of contact hypersensitivity or unresponsiveness to DNFB in Syrian hamsters

The relationship between distribution and function of Langerhans cells within the epidermis and the capacity of cutaneous surfaces to promote the induction of contact hypersensitivity to DNFB have been examined in inbred Syrian hamsters. In a manner very similar to previous findings in mice, the results indicate that hamster cutaneous surfaces deficient in normally functioning Langerhans cells, naturally (cheek pouch epithelium) or artificially (after perturbation with ultraviolet light), are inefficient at promoting DNFB sensitization. Instead, DNFB applied to these regions of skin results in the induction of a state of specific unresponsiveness. Viable lymphoid cells from unresponsive hamsters can transfer the unresponsiveness to naive hamsters suggesting that active suppression is at least partly responsible, probably mediated by T lymphocytes.

Ultraviolet light depletes surface markers of Langerhans cells

This report defines the influence of ultraviolet light (UV) on Langerhans cells (LC). Human volunteers and hairless mice (Swiss ha/ha) were exposed to various single and/or cumulative doses of either UV-A, UV-B, or UV-A plus small amounts of UV-B (UV-A (+B)). 24 hr after the last irradiation, morphology of the entire epidermis was evaluated by both light and electron microscopy while LC, in addition, were tested for expression of specific histochemical (ATPase) and functional immunological markers (Ia antigens). In both men and mice, cumulative doses of either 80-120 J/cm2 UV-A (+B) or 1-2 X 100 J/cm2 UV-A resulted in a dramatic reduction of cells exhibiting ATPase and Ia-reactivity. In the UV-B spectrum, single doses of 60-80 mJ/cm2 produced a virtually complete elimination of LC membrane markers. By contrast, pemphigus antigens of keratinocytes were unaffected by these energy doses. Electron microscopy revealed cellular damage of some LC after UV-doses which produce a virtually complete abolition of LC membrane markers. At certain dose ranges (15-30 mJ/cm2 UV-B and 1 x 40 to 2 x 100 J/cm2 UV-A) LC were the only epidermal cells to display morphological damage at the ultrastructural level whereas higher doses affected all epidermal cells. The finding that LC surface markers and to a lesser extent the cells themselves are particularly susceptible to UV irradiation has important implications in view of previous findings that LC are potent stimulators of antigen-specific and allogeneic T cell activation. UV-induced alteration of LC plasma membrane integrity may represent a tool to manipulate adverse immune reactions involving the epidermis.

Peptide map comparisons of epidermal and spleen H-2 molecules

Peptide map comparisons of molecules encoded in the mouse H-2 complex isolated from epidermal cell preparations have been carried out. We previously showed that the Ia molecules from both the I-A and I-E subregions are synthesized by nonlymphoid bone-marrow-derived cells, probably Langerhans cells. The K and D or transplantation molecules are synthesized by both "true" epidermal cells and nonlymphoid bone-marrow-derived cells. The tryptic maps generated by separating tryptic peptides by high pressure liquid chromatography (HPLC) of epidermal H-2 molecules are identical to their spleen-cell counterparts. The biological significance of this finding is discussed.

Langerhans cells in dermoid cysts: transmission electron microscopic, cytochemical and immunofluorescent observations

Langerhans cells were detected in squamous, stratified epithelia lining human dermoid cysts. Their presence was assayed by ATPase staining and reactivity with heteroantisera against "Ia-like" antigens. Transmission electron microscopic studies demonstrated variations in the numbers of cells showing Birbeck granules in epithelia with different degrees of keratinization. Indeterminate cells (i.e. lacking granules), were more frequent in epithelia showing combined mucous and keratinizing differentiation. Membrane-coating-granules and keratohyalin granules were present in epithelia containing Langerhans cells with clearly identifiable Birbeck granules. Interepithelial mast cells were observed in epithelia with mucous differentiation. A relationship between Langerhans cells and keratinization was suggested. Such non-immune functions are compatible with the known macrophage characteristics of the cell.

A method for quantifying Langerhans cells in epidermal sheets of human and murine skin

Langerhans cells are dendritic cells located in the epidermis. Several techniques have been used previously to stain these cells in sheets of epidermis separated from dermis. The ATPase technique is most commonly used but has several significant defects, the most important being that it is inconstant and nonspecific. Langerhans cells and indeterminate cells are the only dendritic cells in the epidermis which have Ia antigens on their surface. We have adapted an indirect immunofluorescence method to stain this population of cells in epidermal sheets. The technique is sensitive, specific, and can be used to identify and quantify Langerhans cells in human or murine epidermal sheets.

Bone marrow origin of Ia molecules purified from epidermal cells

Using radiation bone marrow chimeras, we have shown that Ia molecules purified from epidermal cell preparations of the mouse reflect the Ia phenotype of the bone marrow donor. This result strongly suggests that Ia molecules are synthesized by a bone-marrow-derived cell in the epidermis. Furthermore, results of peptide map analysis of immunoprecipitated biosynthetically labeled Ia suggest that the Ia molecules found in skin are identical to those found on B lymphocytes. These results support biochemical as well as serologic identity.

Expression of Ia antigens on Langerhans cells in mice, guinea pigs, and man

In all mammalian species so far examined, Langerhans cells or their precursors are the only epidermal cells expressing Ia antigens or their equivalents. In man, xenoantisera raised in rabbits against purified B lymphocyte cell membrane antigens were utilized to stain the Langerhans cells, by either fluorescence or immunoferritin methods. A high proportion of the indeterminate cells in the epidermis also expressed HLA-DR antigens, and a relationship to Langerhans cells is suggested. Confirmation of these results was obtained in mouse. Alloantisera raised against I-A and I-EC subregion products again stained only Langerhans cells. Fluorescence, immunoperoxidase, and immunoferritin methods were used, and confirmation of the specificity of the reaction was achieved at the electron microscope level. Langerhans cells were shown, by ATPase staining, to be absent from the epithelium of the central cornea, but were present in the limbus. Population of the entire corneal epithelium surface was induced by application or irritants or contact sensitizing agents such as dinitrochlorobenzene. Grafting of corneas either deficient or populated with Langerhans cells, to skin beds, may answer the question of the influence of such cells on allograft rejection.

Natural and perturbed distributions of Langerhans cells: responses to ultraviolet light, heterotopic skin grafting, and dinitrofluorobenzene sensitization

Epidermal Langerhans cells exhibit many features of macrophages/monocytes. Both bear surface receptors for the Fc portion of immunoglobulin molecules and the C3b complement component. Both take up, process, and present antigens to reactive lymphocytes in an effective fashion, and they display on their cell surfaces the alloantigenic determinants encoded by the I region of the major histocompatibility complex. In view of these facts, we explored the extent to which cutaneous sites with unusual immunologic attributes might correspondingly have maldistributions or decreased surface densities of Langerhans cells. Common body sites such as the ear, back, and abdominal wall skin in hamsters, mice, and guinea pigs had regularly distributed ATPase-positive Langerhans cells in surface densities between 500 and 1,500 cells/mm2. In contrast, hamster cheek pouch epithelium had fewer than 200 Langerhans cells/mm2 and murine tail skin exhibited both a decreased density and an unusual gridlike distribution of the cells. Langerhans cells were never demonstrated in corneal epithelium. Perturbation of body wall skin with ultraviolet light and with dinitrofluorobenzene temporarily depleted the skin of ATPase-positive Langerhans cells. Heterotopic grafts of hamster cheek pouch and murine tail skin tended to accumulate Langerhans cells and to become more like body wall skin. The concordance of Langerhans cell aberrations and unusual immunologic features of corneal cheek pouches and tail skins suggests the possibility that intentional perturbations of surface Langerhans cells, as with UVL, might achieve unusual immunologic reactions within normal body wall skin.

Langerhans cells: sentinels of skin associated lymphoid tissue

Langerhans-cell-enriched epidermal cell preparations, when pulsed with antigen, can induce proliferative responses, in immune T cells, that are of the same magnitude as those induced by antigen-pulsed macrophages. Additionally, these cells bear surface receptors for Fc and C3b and display on their cell surface determinants encoded by genes of the I region of the major histocompatibility complex. Histological studies have implicated Langerhans cells in cell-mediated immune responses such as delayed contact hypersensitivity to 2,4-dinitro-1-fluorobenzene (DNFB). Langerhans cells play an important role in the induction of contact sensitivity. When murine epidermis that is naturally or artificially depleted of Langerhans cells is painted with DNFB, no sensitization occurs. More importantly, animals whose initial exposure to DNFB occurs through skin deficient in Langerhans cells are unable subsequently to mount effective hypersensitivity responses to this agent. We there believe that Langerhans cells function as peripheral antigen-presenting cells and that in their absence the host responds to antigen challenge by becoming specifically unresponsive.

Tolerance or hypersensitivity to 2,4-dinitro-1-fluorobenzene: the role of Langerhans cell density within epidermis

Epidermal Langerhans cells have been implicated in the process by which animals skin painted with highly reactive haptens, such as DNFB, develop contact hypersensitivity. Compared to normal body wall skin, murine tail skin contains relatively few, unevenly distributed Langerhans cells; ultraviolet light exposure depletes the epidermis transiently of normal numbers of morphologically identifiable Langerhans cells. When mice are painted with DNFB on skin naturally or artificially depleted of Langerhans cells, contact hypersensitivity is not induced. More importantly, these animals become specifically unresponsive to the chemical contact, and are unable to mount effective hypersensitivity reactions if presented subsequently with an immunogenic regimen. It is concluded that Langerhans cells provide the skin with an intricate dendritic network just beneath the keratinized layer, the function of which is to receive, process and present cutaneously applied antigens in an immunogenic form. When this barrier network is breached, the host responds to antigenic exposure by becoming profoundly and specifically unresponsive. Implications of this hypothesis for epidermal virus infections and cutaneous malignancy are discussed.